It is common practice in industry to use adhesive-backed labels bearing indicia such as price, description, or SKU (stock kind unit) number to identify a particular item. As the information printed on the label becomes outdated, the old label must either be removed from the product, or covered over with a label bearing the new information. To ensure that individuals have not tampered with the label, it is desirable that adhesive labels have a security feature that provides visual indication when the label has been tampered with.
The advent and widespread acceptance of universal product code (UPC) scanning technology has placed additional demands on the quality of the labels bearing barcodes. The relative opacity of the label material is an important factor in the scanning quality of the label surface.
For "cover-up" applications, the label opacity is critical. For example, when an old price label is being covered up with a new label, it is important that the old information not be seen through the new label, for customer relation purposes. In industries such as automotive parts and apparel, where inventory is bought and sold repeatedly, it is important that the original or previous label containing old price and/or the previous vendor's name not be visible. In another case, outdated printed indicia on the surface of a packing carton itself may need to be covered up or changed; for example, if boxes for containing a product such as a toy have been prepared and the box artwork must be changed to something more appealing, a cover-up label with the new artwork could simply be affixed over the old, thus eliminating wasteful scrapping of the old cartons.